Data from: Finite-element analysis of microwave scattering from a three-dimensional human head model for brain stroke detection

In this paper, a detailed analysis of microwave (MW) scattering from a three-dimensional (3D) anthropomorphic human head model is presented. It is the first time that the finite-element method (FEM) has been deployed to study the MW scattering phenomenon of a 3D realistic head model for brain stroke detection. A major contribution of this paper is to add anatomically more realistic details to the human head model compared with the literature available to date. Using the MRI database, a 3D numerical head model was developed and segmented into 21 different types through a novel tissue-mapping scheme and a mixed-model approach. The heterogeneous and frequency-dispersive dielectric properties were assigned to brain tissues using the same mapping technique. To mimic the simulation set-up, an eight-elements antenna array around the head model was designed using dipole antennae. Two types of brain stroke (haemorrhagic and ischaemic) at various locations inside the head model were then analysed for possible detection and classification. The transmitted and backscattered signals were calculated by finding out the solution of the Helmholtz wave equation in the frequency domain using the FEM. FE mesh convergence analysis for electric field values and comparison between different types of iterative solver were also performed to obtain error-free results in minimal computational time. At the end, specific absorption rate analysis was conducted to examine the ionization effects of MW signals to a 3D human head model. Through computer simulations, it is foreseen that MW imaging may efficiently be exploited to locate and differentiate two types of brain stroke by detecting abnormal tissues’ dielectric properties. A significant contrast between electric field values of the normal and stroke-affected brain tissues was observed at the stroke location. This is a step towards generating MW scattering information for the development of an efficient image reconstruction algorithm.本文针对三维（three-dimensional，3D）拟人化人头模型的微波（Microwave，MW）散射现象开展详细分析。这是首次将有限元法（Finite Element Method，FEM）应用于针对脑卒中检测的三维写实人头模型的MW散射特性研究。相较于现有公开文献，本文的核心贡献在于为人头模型赋予了解剖学层面更逼真的细节特征。本研究依托磁共振成像（Magnetic Resonance Imaging，MRI）数据库构建三维数值人头模型，并通过创新性组织映射方案与混合模型方法将其分割为21类不同组织，同时采用同一映射方案为各脑组织赋予非均匀频散介电特性。为匹配真实仿真配置，本研究采用偶极天线设计了环绕人头模型的八元天线阵列。随后针对人头模型内部不同位置的两种脑卒中类型——出血性（haemorrhagic）与缺血性（ischaemic）——开展检测与分类可行性分析。本研究采用有限元法求解频域亥姆霍兹波动方程（Helmholtz wave equation），进而计算透射信号与后向散射信号。为在最短计算耗时内获得无误差的仿真结果，本研究还开展了电场值的有限元网格收敛性分析，并对不同类型的迭代求解器进行了对比测试。最后，本研究开展了比吸收率（Specific Absorption Rate，SAR）分析，以探究MW信号对三维人头模型的电离效应。通过计算机仿真结果可知，通过检测异常组织的介电特性，MW成像技术可有效实现两种脑卒中类型的定位与鉴别。在脑卒中病灶位置，正常脑组织与卒中受累脑组织的电场值存在显著差异。本研究为开发高效图像重建算法所需的MW散射信息生成工作迈出了关键一步。